// Press Shift twice to open the Search Everywhere dialog and type `show whitespaces`,
// then press Enter. You can now see whitespace characters in your code.
public class Main {
    public static void main(String[] args) {
        double sum = 0,a = 1;
        int i =1;
        while(i<=20){
            sum = sum +a;
            i++;
            a = a*i;
        }
        // Press Alt+Enter with your caret at the highlighted text to see how
        // IntelliJ IDEA suggests fixing it.
        System.out.println("sum="+sum);


    }
}